From: Jaegeuk Kim Subject: Re: [f2fs-dev] [RFC PATCH 10/10] f2fs: fs-verity support Date: Tue, 28 Aug 2018 18:43:47 -0700 Message-ID: <20180829014347.GA27219@jaegeuk-macbookpro.roam.corp.google.com> References: <20180824161642.1144-1-ebiggers@kernel.org> <20180824161642.1144-11-ebiggers@kernel.org> <20180826173507.GC728@sol.localdomain> <20180828072756.GC29049@jaegeuk-macbookpro.roam.corp.google.com> <63a19512-e938-d239-9e3c-f6ecc479478c@huawei.com> <20180828170142.GB62482@jaegeuk-macbookpro.roam.corp.google.com> <8b7f83db-810a-bdd6-85b0-1248dc14f8d7@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Chao Yu , Eric Biggers , Dmitry Kasatkin , Michael Halcrow , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-ext4@vger.kernel.org, Mimi Zohar , Victor Hsieh To: Chao Yu Return-path: Content-Disposition: inline In-Reply-To: <8b7f83db-810a-bdd6-85b0-1248dc14f8d7@huawei.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On 08/29, Chao Yu wrote: > On 2018/8/29 1:01, Jaegeuk Kim wrote: > > On 08/28, Chao Yu wrote: > >> On 2018/8/28 15:27, Jaegeuk Kim wrote: > >>> On 08/27, Chao Yu wrote: > >>>> Hi Eric, > >>>> > >>>> On 2018/8/27 1:35, Eric Biggers wrote: > >>>>> Hi Chao, > >>>>> > >>>>> On Sat, Aug 25, 2018 at 01:54:08PM +0800, Chao Yu wrote: > >>>>>> On 2018/8/25 0:16, Eric Biggers wrote: > >>>>>>> From: Eric Biggers > >>>>>>> #ifdef CONFIG_F2FS_CHECK_FS > >>>>>>> #define f2fs_bug_on(sbi, condition) BUG_ON(condition) > >>>>>>> #else > >>>>>>> @@ -146,7 +149,7 @@ struct f2fs_mount_info { > >>>>>>> #define F2FS_FEATURE_QUOTA_INO 0x0080 > >>>>>>> #define F2FS_FEATURE_INODE_CRTIME 0x0100 > >>>>>>> #define F2FS_FEATURE_LOST_FOUND 0x0200 > >>>>>>> -#define F2FS_FEATURE_VERITY 0x0400 /* reserved */ > >>>>>>> +#define F2FS_FEATURE_VERITY 0x0400 > >>>>>>> > >>>>>>> #define F2FS_HAS_FEATURE(sb, mask) \ > >>>>>>> ((F2FS_SB(sb)->raw_super->feature & cpu_to_le32(mask)) != 0) > >>>>>>> @@ -598,7 +601,7 @@ enum { > >>>>>>> #define FADVISE_ENC_NAME_BIT 0x08 > >>>>>>> #define FADVISE_KEEP_SIZE_BIT 0x10 > >>>>>>> #define FADVISE_HOT_BIT 0x20 > >>>>>>> -#define FADVISE_VERITY_BIT 0x40 /* reserved */ > >>>>>>> +#define FADVISE_VERITY_BIT 0x40 > >>>>>> > >>>>>> As I suggested before, how about moving f2fs' verity_bit from i_fadvise to more > >>>>>> generic i_flags field like ext4, so we can a) remaining more bits for those > >>>>>> demands which really need file advise fields. b) using i_flags bits keeping line > >>>>>> with ext4. Not sure, if user want to know whether the file is verity one, it > >>>>>> will be easy for f2fs to export the status through FS_IOC_SETFLAGS. > >>>>>> > >>>>>> #define EXT4_VERITY_FL 0x00100000 /* Verity protected inode */ > >>>>>> > >>>>>> #define F2FS_VERITY_FL 0x00100000 /* Verity protected inode */ > >>>>>> > >>>>> > >>>>> I don't like using i_advise much either, but I actually don't see either > >>>>> location being much better than the other at the moment. The real problem is an > >>>>> artificial one: the i_flags in f2fs's on-disk format are being assumed to use > >>>> > >>>> Yeah, but since most copied flags from vfs/ext4 are not actually used in f2fs, > >>>> also 0x00100000 bit is not used now, so we can just define it now directly for > >>>> verity bit. > >>>> > >>>> Cleanup and remapping in ioctl interface for those unused flags, we can do it > >>>> latter? > >>> > >>> No, it was reserved by f2fs-tools, > >> > >> That's not a problem, since we didn't use that reserved bit in any of images > >> now, there is no backward compatibility issue. > > > > We're using that. > > Oops, if it was in production, I agree to keep it in i_advice, otherwise, we > still can discuss its location. > > > > >> > >>> and I think this should be aligned to the encryption bit. > >> > >> Alright, we could, but if so, i_advise will run out of space earlier, after that > >> we have to add real advice bit into i_inline or i_flags, that would be a little > >> weird. > >> > >> For encryption bit, as a common vfs feature flag, in the beginning of encryption > >> development, it will be better to set it into i_flags, IMO, but now, we have to > >> keep it as it was. > >> > >>> Moreover, we guarantee i_flags less strictly from power-cut than i_advise. > >> > >> IMO, in power-cut scenario, it needs to keep both i_flags and i_advise being > >> recoverable strictly. Any condition that we can not recover i_flags? > > > > In __f2fs_ioc_setflags, f2fs_mark_inode_dirty_sync(inode, false); > > Ah, that's right, do you remember why we treat them with different recoverable > level? Since I thought that such the flags wouln't be critical on power cuts, but be enough for us to guarantee by write_inode() or fsync(). > > Thanks, > > > > >> > >> Thanks, > >> > >>> > >>>> > >>>> Thanks, > >>>> > >>>>> the same numbering scheme as ext4's on-disk format, which makes it seem that > >>>>> they have to be in sync, and that all new ext4 flags (say, EA_INODE) also > >>>>> reserve bits in f2fs and vice versa, when they in fact do not. Instead, f2fs > >>>>> should use its own numbering for its i_flags, and it should map them to/from > >>>>> whatever is needed for common APIs like FS_IOC_{GET,SET}FLAGS and > >>>>> FS_IOC_FS{GET,SET}XATTR. > >>>>> > >>>>> So putting the verity flag in *either* location (i_advise or i_flags) is just > >>>>> kicking the can down the road. If I get around to it I will send a patch that > >>>>> cleans up the f2fs flags properly...> > >>>>> Thanks, > >>>>> > >>>>> - Eric > >>>>> > >>>>> ------------------------------------------------------------------------------ > >>>>> Check out the vibrant tech community on one of the world's most > >>>>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot > >>>>> _______________________________________________ > >>>>> Linux-f2fs-devel mailing list > >>>>> Linux-f2fs-devel@lists.sourceforge.net > >>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > >>>>> > >>> > >>> . > >>> > > > > . > >